Erm, "Linux" is released under the GPL. (
www.gnu.org for info on the licence)
www.ubuntu.com
www.debian.org
fedora.redhat.com
Are 3 distributions.. there are hundreds of distributions, tho.. all based around the Linux kernel.
If you just wanna try it out, I'd recommend
www.ubuntu.com - it's about the best you'll get in terms of a desktop
I've used Debian for years (8-9 years or something. Both professionally and personal usage, day in, day out) and that's what I use on servers (Again, everyday.). I don't run Linux on desktop/laptops now.. as I still don't think it's up to the standard of Windows or OSX for this usage. On a server, it's unrivalled IMO, but desktop usage.. no. I used it on my desktop for years, and on my laptop recently.. and it's OK but I had to do some pretty weird things to get stuff working - like, writing scripts to get Wireless working as the GNOME app (Network Manager) didn't work properly - It should be OK now tho.. but, you'll always tend to find something doesn't work and needs some weird workaround, which never is as good. Again, I don't mind it on servers as it's all console based anyway (I run all my servers via SSH) but on a desktop/laptop, I always felt things should "just work" so you can "just do stuff" without messing around beforehand.
I guess it depends how much you wanna play around or just get stuff done
OSX is perfect really.. all the power of a Linux distribution, but all the polish and finish of a proper OS.. and that's what makes the difference on a machine you are *using* to do work. My OSX box has a terminal and all the apps I use regularly in Linux.. but, of course, it also has the finished product feel
Anyway, if you wanna play.. Ubuntu gets my vote
However, if you want a "Windows" replacement for your desktop, OSX on a Mac is right up there..
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