The rights to your ideas depend on the project type.
When you submit an idea on jovoto, the rights to your work remain yours. Only if your idea is licensed by a client, are the rights to your work transferred. To ensure that the client has enough time to decide, there is a client exclusivity period for each project. During this time as designated in the brief and Project Terms (usually 3 or 6 months), you cannot offer your design/concept to other parties.
Read about how licensing works on jovoto.
By agreeing to the "Work contract" in Invite Projects all rights automatically get passed to the client.