You're assuming you will be able to get a single data file, upload that to roll20, and voila, instant compendium. I cant imagine why you'd think it would work this way. We will have to enter data manually - look at how characters, tables, and everything else in roll20 is created. The roll20 devs have said they are interested in giving us custom compendiums, and the main stumbling block is how hard the tools are to use. Roll20 has always erred on the side of copyright protection, they have definitely considered this and are willing to go ahead. So the copyright issue should be a non-issue, because they would never do it if they weren't satisfied. Look at how difficult it is to share characters between different GM's campaigns (especially if you arent a Pro user). Technically, these are just data in a database, but we can't get at it in an easy way (even if you are a Pro user and want to use the API to copy characters out is an extremely arduous manual task). The compendium is going to be much the same. My guess is, custom compendiums are going to be isolated to individual GM's campaigns in the same way, with you manually creating each item, and will be a very tedious manual process to get stuff out. But whatever the case, arguing over copyright concerns really is a dead end. The devs have said they want to give us custom compendiums, we can leave them to sort out the details and handle that aspect of it.