And Source SDK Base 2006 based mods too. On the other hand, just as P(PORTAL)RTAL said, there’s no base for Source Engine 2009 (HL2, Episodes, Portal, CSS, TF2, etc), so the only way for mod to use SE 2009 is to be based on one of these games.
To Dias
To be honest, I’m waiting for BMS since 2006, but I was too lazy to re-register after forum 2009 crash. 
You’ve only made 2 posts so far, but I already like you. You clearly know your shit. 
This might be a little off, but Portal 2 has a newer version of Source and it’s source SDK is not yet avaible, am I right?
On: In my country, games are really expensive, but technically downloading them is not illegal (only uploading them is)… still, many years ago I did buy Half-Life 2 (later Episode One’s box, than Orange Box, and most recently Portal 2, all legal) , reasoning, that it’s not just one game, but with it I’ll also gain access to a lot of good mods too.
Medkit
Well, Portal 2 really uses upgraded version of Source Engine 2, but Portal 2 Authoring Tools (Beta) is available on Steam (you must own Portal 2 to install).
As for free SDK and bases, it looks like new VALVe’s politics against pirates who crack their games and Steam platform at all. So, now customers have choice - to play games and mods legally with full tech support via Steam forums, or to play ripped games and mods “as is” with [possible] bugs and without any support. IMO, any intelligent person will choose the first.
Damn right. Sadly, there are some poor (or just dumb) fuckers who actually don’t pay for their games. Well, let them rot in their non-updated hell.
@Calhoun Freeman: Damn straight - I honestly want to print that out and wallpaper it all over my living room.
Portal 2 doesn’t use Source engine 2 but a updated engine version. Valve has said that they won’t make a Source engine 2. They will just keep updating Source.
Jack Freeman
When I said ‘Source Engine 2’ I meant Source Engine with VPK support. Ofc it’s just upgraded one, not one redone from scratch.
I have an old HL2DM and Portal account. I got both for free and I wasnt able to play any mods until Source SDK became free. A few days ago, I’ve started Firearms :s ource on that account and it worked 
I guess it depends on the actual mod, whether it can be played or not. Portal Prelude for example needs Portal, because of textures.
I hope that Valve will make it possible to ban griefers even if they use multiple accounts to play.
Valve has impeccable timing.
Sry for bumping this up, but would it not make sense to update the about page and the system requirements on the wiki? It still says, that a purchased Source Engine game is required to play Black Mesa, which isn’t true anymore.
Just because a Source game (TF2) is free now doesn’t necessarily mean it comes with the SDK base which is what is required to play the mod. There was a bunch of arguing about this before and I’m not exactly sure what the consensus is. I suppose you’d just have to wait till the mod is released and try it for yourself. It would be weird that someone interested in this game doesn’t have a single Source game though.
Well, someone only would have to create a new Steam account and watch, if the Source SDK Base is available and try it out with any mod that only uses the SDK content. I would do it by myself, but I have a bad Internet connection at the moment.
I think that doesn’t really matter.
The way I understand it is: Full-conversion mods like Black Mesa will almost certainly be playable by everyone. Certain mods that use a lot of content only available in certain games (ie, most HL2 “level expansions” that are mostly just new levels) may not be playable.
Of course, this information is drawn from my logic, not from the fact that I’m a developer.
I’m able to play Zombie Panic: Source on such a new Steam account (after installing TF2). Maybe that helps a little.
I’ve created a new account without any purchased game and I have full access to the Source SDK Base and Source SDK 2007!
So, why aren’t you updating the outdated information on the system requirements page already?
They got other more important stuff to do.
Because as is, it encourages people who doesn’t have a source-game, to purchase one. Which I believe is a nice gesture towards valve. But perhaps that’s just me.
seriously? no offense but that wouldn’t even take 5 minutes to update (not that I would care if it gets updated).
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.