It's that time of year when licenses expire, as seen with Activision and Capcom's recent delistings, and I guess it's Sega's turn. I didn't think that these would get taken down while Isolation was still new, but apparently there were separate licenses that Sega didn't want to keep.
Nuuvem still has AvP for dirt cheap (less than $1.50), if you want to get it while you have the chance: http://www.nuuvem.com.br/produto/72-aliens-vs-predator
And if you really still want Colonial Marines, Amazon has it for just over $5: http://www.amazon.com/dp/B009K6YJTS/?tag=neogaf0e-20
(Both of the above links are Steam keys.)
AvP Classic is unaffected, which probably has to do with it being published by Rebellion itself.
Nuuvem still has AvP for dirt cheap (less than $1.50), if you want to get it while you have the chance: http://www.nuuvem.com.br/produto/72-aliens-vs-predator
And if you really still want Colonial Marines, Amazon has it for just over $5: http://www.amazon.com/dp/B009K6YJTS/?tag=neogaf0e-20
(Both of the above links are Steam keys.)
AvP Classic is unaffected, which probably has to do with it being published by Rebellion itself.