Feel free. The legal implications are (keeping in mind that I'm not a lawyer, I just selected the licenses):
You agree your contribution can be edited, deleted, remixed, changed, ignored, and so on, and it can be published along the terms of the two licenses of the project. We don't have exclusivity at all - you can publish them here and then use them again in your own projects however you want (for pay or not). Best of all, if someone writes something cool in the project that relates to your contribution, you can use it in your own project as long as you credit the Great Hundred under the terms of either license.[sblock=more detail on Creative Commons attribution]You agree to release your contribution as part of the project under Creative Commons - Attribution. This means that people can use, remix, and share however they like, including for commercial purposes. This means someone could write a game or book based on the setting / your idea - and they can publish it without asking for permission or sending any cash your way. The only requirement is that they give credit the project (the project will have its own credits page listing the non-spamblocked contributors to the wiki). This was adopted to encourage professional creative people to participate (those who appreciate the Creative Commons but not necessarily know about the OGL).[/sblock][sblock=More detail on the OGL]You agree to release your contribution as part of the project under the OGL. This means that people can use, remix, and re-use the material, including for commercial purposes. This means someone could write a game or book based on the setting / your idea - and they can publish it without asking for permission or sending any cash your way. The only requirement is that they append an OGL to their document and give credit to the project in the OGL's section 15 (the project will have its own credits page listing the non-spamblocked contributors to the wiki). This was adopted to encourage professional game industry people to participate (those who appreciate the OGL but are not necessarily comfortable with the Creative Commons).[/sblock][sblock=more detail on the two licenses working together]The document, when released, will be released twice, once as CC-Attribution, once as 100% Open Game Content under the OGL. That means that people can use it under either license - if you're not comfortable with the Creative Commons or don't think it's a good license, you can just use material from the Great Hundred under the terms of the OGL. The converse is also true.[/sblock]This means someone else could write a game based on the setting such as a game based on the setting, or a novel that incorporates the idea you originally contributed, and they can sell their game or novel for money. This is important so that professional contributors don't have to worry that they're limiting their options later by contributing good ideas they have now.