This is the version of Legacy that includes all files you will need.  Follow the following instructions:

Simply run the UMOD and click on "Enable OldSkool Amp'd" (in the modmenu) and Legacy is fully installed!  Then start a new single player game, and select Legacy.  Read up on the Legacy documentation for more details.

OldSkool Amp'd notes:
The UMOD includes a stripped-down version of OldSkool Amp'd 2.10.  It has all the features of the full, simply many are left unreferenced.  You can, however, use this version to upgrade your existing OldSkool, and no features will be lossed.  OldSkool Amp'd 2.20 will come out shortly, featuring all of the things found in this update and more!  If you wish to have the other features download from UsAaR33's site:
http://www.unreality.dk/usaar33
If you run the UMOD (at 2.05), you will need to install Legacy again, to upgrade to 2.10.  (note that Legacy will work on any version of oldskool)
It is also important to note that CSHP NO LONGER FALSELY DETECTS OLDSKOOL AS A CHEAT.  Thus, OldSkool is 100% safe to have now.

Please check http://www.unreality.dk/usaar33 for updates and to see if this announcement changes.