The short answer is yes! All the sound effects available for download on freeSFX are uploaded by the owners of the sounds who have granted permission for them to be downloaded and used.
The sound effects we provide can be used in any commercial, non-commercial, broadcast multimedia/audio visual production. Certain restrictions are in place on how the sounds can be used which can be viewed in our End User Licence Agreement
Unfortunately, no. We used to allow this but there were so many people uploading sounds they did not have the rights to that we have had to disable this option. Only invited users will be able to upload new sounds to the site.