From IV:MP Wiki
Q: What is IV:MP?
A: IV:MP is a modification for the game Grand Theft Auto: IV that adds an alternative multiplayer which features online play with various custom modes.
Q: Where can I download it?
A: You can find the latest version on http://iv-multiplayer.com if there is one.
Q: Does it cost?
Q: Will I be able to play with my pirated version of GTA:IV?
A: We will not support pirated versions.
Q: What's with the servers? Is it going to be like GTA:IV's original servers?
A: There will be dedicated servers available, running custom scripts.
Q: What patch do I need to run it?
A: Currently, only patch 7 (18.104.22.168) is supported.
Q: What about GFWL?
A: IV:MP does not rely on GFWL.
Q: Can I play with my steam version?
Q: Are you the people who develop SA:MP?
A: No, We are not affiliated with neither SA:MP nor the SA:MP Community in any way.
Q: Is it IV:MP or IV-MP?
A: Originally, it's IV:MP.
Q: What script language will be used?
Q: When will it be done?
A: When it's finished.