I'm stuck with a tough decision. With the release of Alien Swarm, I could make the mod freeware, not requiring any half life games, with the same graphical quality as an orange box mod. Moreover, the user interface would benefit much from switching to Alien Swarm codebase. But, this would mean more work to create basic props, textures, and sounds, since we won't be able to use those from hl2's resources.
Both Alien Swarm and Half-Life 2 Ep2 run on the source engine, which mean that porting is very easy. However, I don't know the limits of the codebase for Alien Swarm yet. I don't even know yet if I'll be able to use the multiplayer feature of ASW, because of the quirks of the current release of the sdk.
I guess I'll have to find out by testing ASW's limits.
Disclaimer: This mod isn't in any ways endorsed, funded, licensed, authorized, or related to/by Nintendo. All characters and elements of the StarFox franchise belong to Nintendo. No assets from Nintendo games have been used, all content is fan made. This mod is not made for profit, or to profit from Nintendo's properties, or to interfere with Nintendo's business. It is a work of fan fiction, in which Nintendo's characters are put in situations/described or represented in a way, not necessarily intended by the author / owners. It is made simply to share products of fan imagination, for the educative experimentation of game development, and to pay homage to this Nintendo franchise.