And remember, any mod for the "mods" directory have NO Mojang code in them, with applies to Redpower 2, IC2, ThaumCraft 2, BuildCraft (and a long time ago better then wolves mod LOL)
The developers of those mods are still familiar with Minecraft, so their work is "contaminated". In order to claim ownership of the copyright, they must prove "independent invention". The only way I know of to accomplish this is with the clean room design pattern, which involves a "contaminated" reverse engineer generating detailed specifications, a highly qualified copyright lawyer inspecting and approving the specifications, and finally an "uncontaminated" software developer to write the code. This most likely means that the only people who can write mods for Minecraft and claim copyright are people who have never played Minecraft before.
Thus, mod writers are, from a purely legal perspective, infringing Mojang's copyright. Fortunately, Mojang seems to be turning a blind eye towards mods for now, so nobody is going to get sued (phew!). However, Notch has stated he has mixed feelings about mods as they currently are, which is why Mojang is working on providing an API for mods to use. MOST LIKELY, once the API has been provided Mojang will start cracking down on mods which infringe their copyright! This means Forge (and all Forge related mods) are going to die, unless the API can provide the same functionality.
Anyways, even though I was introduced to Minecraft mods via Technic, I was disappointed to learn that they did not get permission to redistribute the mods. I follow direwolf's installation instructions now.