Hello,

the problem seems that your MySQL is not configured to support long primary keys.
Normally this is the default can be changed by phpmyadmin or by the hosting itself.

To fix you could try to change the query for tables to not exceed your limit and change from 255 to a lower limit for example 100 such as the following:

CREATE TABLE IF NOT EXISTS `#__jchat_banned_users` (
`banning` VARCHAR( 100 ) NOT NULL,
`banned` VARCHAR( 100 ) NOT NULL,
PRIMARY KEY (`banning`, `banned`)
) ENGINE=InnoDB CHARACTER SET `utf8`;

CREATE TABLE IF NOT EXISTS `#__jchat_public_sessionrelations` (
`ownerid` VARCHAR( 100) NOT NULL,
`contactid` VARCHAR( 100) NOT NULL,
PRIMARY KEY (`ownerid`, `contactid`)
) ENGINE=InnoDB CHARACTER SET `utf8`;


CREATE TABLE IF NOT EXISTS `#__jchat_webrtc` (
`peer1` VARCHAR( 100) NOT NULL,
`peer2` VARCHAR( 100) NOT NULL,
`sdp` TEXT NULL,
`icecandidate` TEXT NULL,
`videocam` tinyint(4) NOT NULL default '1',
PRIMARY KEY (`peer1`, `peer2`)
) ENGINE=InnoDB CHARACTER SET `utf8`;

CREATE TABLE IF NOT EXISTS `#__jchat_webrtc_conference` (
`peer1` VARCHAR( 100) NOT NULL,
`peer2` VARCHAR( 100) NOT NULL,
`sdp` TEXT NULL,
`icecandidate` TEXT NULL,
`videocam` tinyint(4) NOT NULL default '1',
`other_peers` TEXT NULL,
PRIMARY KEY (`peer1`, `peer2`)
) ENGINE=InnoDB CHARACTER SET `utf8`;

CREATE TABLE IF NOT EXISTS `#__jchat_webrtc_blackboard` (
`peer1` VARCHAR( 100 ) NOT NULL,
`peer2` VARCHAR( 100 ) NOT NULL,
`sdp` TEXT NULL,
`icecandidate` TEXT NULL,
PRIMARY KEY (`peer1`, `peer2`)
) ENGINE=InnoDB CHARACTER SET `utf8`;

Regards