Do I need to purchase HL2 to access the sdk and develop DOD:S maps? If so, are there any similar limitations concerning the various HL2 releases?

Thanks.

You need to buy at least DODS, the SDK is free but the content is not I think. But with DODS it uses a lot of HL2 textures (AFAIK) so you would be better off getting HL2.

the silver package is well worth its price, and it may entitle you to free content in the future. :)

As Watchtower says, Silver was always the way to go, it answers all your questions on SDK availability tinfoil

there is no more silver package? ^^

the package which now is the counterpart is the "Valve complete pack" and costs 79,95$ ....

So I really hope the SDK will be free if you possess any Source game.

I already bought DOD:S, but I can't seem to get started on setting up a mapping environment. Everyone is talking about the sourcesdk_content folder and downloading through steam.
Although I bought DODS, I do not see any sdk downloading options anywhere.
I've made maps before with WorldEdit (now Hammer apparently), but this steam business looks pretty limiting in the first place.

I might go buy HL2 in the store, without DOD. As suggested I hope this will extend my options, plus the ability to play third party mods (what's HL without them).
Would this be equal to a silver package? I don't want to pay twice for the stuff I already own ...