Well, there is a story behind it all.
Adobe created PostScript. As you know, PostScript is amazing. Part of the big postscript (which I will no longer properly capitalize cause it's annoying) picture was Adobe's fonts. There were, if memory serves correctly, four types, but really only two mattered: Type 1 and Type 3.
Type 3 were bitmap fonts. Nothing really special about these, just a bunch of dots. Bitmap fonts don't scale well: try to expand them and they get blocky, try to shrink them they get illegible. You need a set of bitmap fonts for every point size you want to use. Like I said, nothing special. Adobe didn't care too much about these and let anyone use them. They are fine for printing, not good for screens.
Type 1 fonts were scalable fonts. These were really amazing little buggers because they were defined by their outlines and mathematically splined using a thrid order polynomial (ax^3+bx^2+cx+d) producing smooth shapes nomatter what size they were at. You only needed one Type 1 font to do all sizes. They worked for printing and screens. Adobe was the
only company, in the world to have this technology.
Adobe gaurded Type 1 font technology very closely. It was very expensive to licence it, but, after all, it was the only game in town.
Apple wanted scalable fonts but didn't want to pay Adobe's fees, or have a core OS component controlled by a 3rd company, so they decided to develop their own alternative: TrueType. MS got a royalty-free, perpetual licence to use. I've heard that MS and Apple were working together on it, but quite frankly I have no idea what MS contributed, if anything, and it seems to me like MS really got the better end of the deal.
TrueType works like T1 fonts in that they are outline fonts and are scalable. They are technically inferior in the curve fitting because they only use second order polynomials, but this doesn't seem to matter for the screen. The TT spec allows the font designers to throw "hints" into the font, or little helper instructions to make the font look better at certain sizes according to the font designers eye, rather than a purely mathematical scaling. Using these hints is patented by Apple. Code exists for it in the FreeType library, but it is disabled. You can enable it at compile-time if you licence the patent from Apple. Apple didn't threaten anyone over this, rather FreeType found out about the patent, asked Apple if it would be ok for them to use hinting, got no response, and disabled the code to be safe. I don't think the hinting is that necessary... it's only useful at certain scales, and from what I hear it's bloody hard to program---more of an art form---so not many fonts really use it right.
A nice thing about TT is that they live in just one file. T1 require two files: the font file and the font metrics file. From what I have read, professional typographers consider TT to be inferior to T1.
I myself like T1 fonts. They just feel a little better to me.
Anyway, back to the story.
We now have TT, and it's a much more open specification than T1. The two biggest personal computer platforms, Apple and Windows 3.x use TT. Others are using T1 (OS/2 I know, I think NeXT had the capability because they used display-postscript). You could get T1 fonts to work on Windows and MacOS by installing Adobe Type Manager (ATM), but it wasn't free, and only came with an Adobe product.
So TT was gaining alot of market share, not great for Adobe.
Eventually, T1 lost so much market share to TT, that keeping a lock on T1 made no sense. How are they going to sell their T1 fonts if nobody uses T1?
Adobe opened the T1 spec. Linux uses it as a result. Adobe made ATM a free download.
This is why MS did not make T1 fonts. They don't do it now, although they could. They did this OpenType partnership thing with Adobe which was supposed to sort of unify T1 and TT, but that hasn't seemed to have made a big impact.
Nimbus-Sans is a T1 font, using T1 font specs, but has no Adobe code in it.
Why did MS make that ugly Arial by bastardizing Grotesque into Helvectica's dimensions instead of cloning Helvectica? Well, I can only guess.
Back in the 90's there were sort of "font wars" happening. Alot of small font firms were popping up and making fonts that looked very much like those of the big font houses like Adobe and Monotype, and selling them for much less money. Many of these were inferior to some degree, but many were still really nice.
Some of the really crappy companies had apparently truly ripped off the big font companies by taking the high Q T1 fonts and mathematically converted them to low quality TT fonts before reselling them. Others had built lookalikes from scratch.
Anyway, the big font companies didn't like this. There were lawsuits. Lots of them. Some of these font companies were real bastards. I read one page where a font company saw a decorative font in a jpeg on this guys webpage, checked their records, found they never sold him a copy of their $150 font, and told him they wanted money. He told them the font in the jpeg came from a CD that came with his printer, and gave him the font foundry and name. They then wrote back and said that the font foundry had illegally made a lookalike and demanded he pay them for the font.
Many of those smaller font foundrys are not around anymore.
MS probably wanted to avoid this, so they made a font that was different enough from helvectica that they wouldn't get sued, but would have the same dimensions so it could be a drop in replacement. Thus we get Arial.
I don't know the whole story behind Nimbus-Sans. I know it's a
beautiful donated T1 font from a company. Maybe it's one of the scratchbuilt fonts from a company that survived the font wars (pure speculation, I don't have time to research it now).
