Self hosted Webinar Software

We need custom webinar software and/or education on how to host this successfully. We understand that we may need multiple dedicated servers, which we have. We are currently using Adobe Connect with a 1,000 user max. We would like to be able to have 2000+ consecutive users. We would like to purchase the software and host the meetings without monthly fees (besides hosting) Also, if you know of some software that exists, we will pay for your information. We just need something ASAP. Thank you.