Is it legal to use BMS textures?

I’m making a map for CSGO, which is Half life themed, and i need textures. I saw a guy using BMS textures, so the question is that is it legal to use BMS textures in another game?

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You can use them, but only for non-commercial purposes.

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.