What is Google2SRT?
Google2SRT is a tool that can download "not embedded" subtitles (Closed Captions - CC) from YouTube/Google Video videos (if those are present) and convert them to a standard format (SubRip - SRT) supported by most video players.
Even today, YouTube/Google Video "not embedded" subtitles (CC under their terms) can't be downloaded in a simple way. Even if those are downloaded, they aren't usable in any video player (software or home video player) because they are encoded in a Google's own format.
That's why Google2SRT let download and convert them to a recognized format by most video players (SRT) and that can be converted to another also well-known formats like SSA (SubStation Alpha) or SUB (MicroDVD) by using other software available on the Internet.
Why would I want to download subtitles from YouTube or Google Video?
You may have a video whose subtitles are really hard to find or if you have found them, they aren't available on your language, but there is an available version of the subtitles you are looking for on YouTube/Google Video. Or it's possible you like a video and it's only available through YouTube/Google Video and it's "not embedded" subtitled.
At first, you may think these are really very unusual situations, but certainly they are not. There are free distribution videos, like some documentaries and conferences, or official distributed videos that a TV channel publishes on his own YouTube space, which can be only found through YouTube/Google Video, and their subtitles are not embedded. Not embedding subtitles is an advantage for the provider. Provider only needs to upload a single video and he can offer to select one of many subtitles (or none of them). Some examples are Zeitgeist documentary, Randy Pausch last lecture: "Achieving Your Childhood Dreams" conference, Fullmetal Alchemist: Brotherhood anime, some Top Gear broadcast from the BBC or Google2SRT video demonstration itself.
Under what conditions can I use this software?
Google2SRT is free software (in two senses), licensed under the GNU General Public License (GPL). In brief: you can download, copy, modify, give and sell this software like you want and to who you want, as long as you distribute original source code and, if you modify or reuse Google2SRT source code, also the new source code and under the same conditions.
Why this name? What does it mean?
Hmmm... Unfornately for me (and for my imagination) all software must have a name with which it will be called. There are developers who "live" with their software and name it with names so metaphorical like Windows, Photoshop, Mac(intosh) or eMule. There are other type of developers which don't go so far and we simply call it with a less comercial but clearer name (for ourselves, the authors, of course). Then, Google2SRT means "Google to SRT", "from Google's format to SRT format". YouTube is Google's property too and it has inherited subtitles format.