ER/Builder Data Modeler is free for personal use, the commercial version is scheduled for early 2019. It allows developers to design or modify databases and supports creating entity relationship diagrams.
Supported databases: Oracle, MS SQL Server, PostgreSQL, MySQL, SQLite and Firebird.
Ranked in these QuestionsQuestion Ranking
Only 8 Mb install size.
Pro Ease of use
Pro Not limited
The free version does not seem limited (for personal use).
Con Virus alert
Avast antivirus gave a false virus alert, this is probably because the application is unknown and not yet widely used.
Con Relation arrows
The arrows between tables do not indicate the kind of relation, like a crowfoot symbol for 1:n relationship.