It might take a day or two to be granted editor permissions, but then it will probably take less than an hour to learn how to start to be able to contribute to Lingopolo as an editor. Sure, some of the more complex tasks (like creating and editing sound files) might need a bit more time to learn, but generally speaking it's been made relatively easy to contribute.
Once you have learnt how to edit, you can then contribute whenever you get a spare ten minutes. Of course you can spend longer contributing at any given session, but even if you only spend half an hour when you have time, you can make a valuable contribution.
There is no long-term commitment required.
In summary, it will take you about an hour to get up and running, and then you can contribute as much as little as you want, for as long or as short as you want.