Sun Microsystems 'was' one of the biggest competitors of Microsoft in open source world. It is true they ruled the world with Java and its bi-products but when Microsoft challenged the rule of Java on internet by introducing .Net framework and a new Java like language C#, Sun became more open. Whether it was a business decision or it was really the love of open source world that Sun opened up regarding Java. Sun opened up Java round about 3 years ago. Sun was the biggest contributor to OpenOffice.org, the one and only open source office suit which can some how face MS Office. Sun was going well and every thing was going happily. But........ real world is not like the stories of princes and princesses who live happily always, so Sun had to face the challenge. A big fish Oracle proposed Sub to be eaten, and Sun agreed. And now Sun is gradually being eaten by Oracle.
That is the fate of small companies that they are eaten up or in more 'technical terms' acquired by bigger ones. First MySql was acquired by Sun and then Oracle acquired Sun. And the result was that the only open source and low cost competitor of Oracle Enterprise Database is no longer harmful for Oracle. Because they are now (step) brothers. Though Oracle is promising to run MySQL as it was run previously but they are in better ever position to keep MySQL 'on track' now.
Java is something for which Sun is known in the open source world, specially after the opensourcing of Java. Java introduced new competing technologies under the banner of Sun as JavaFX. But it is moving slowly since a year or so, obviously it is due to the replanning which is taking place in Sun after the acquisition by Oracle.
Open Solaris is a Unix like operating system and again it was open source. But the community governing the matters of Open Solaris is now being frustrated by the silence of Oracle regarding the future of the operating system. Would it be of worth for Oracle in the case that they already have a fork of Redhat Enterprise Linux names Oracle Unbreakable Linux. Well, people at Open Solaris community are even willing to fork the project and continue it independently. Whether it would be good or bad, or whether Open Solaris would continue its existence or die slowly, the time will tell about it.
Sun was a big contributor to open source OOo, Java, Open Solaris and MySQL are now looking at Oracle for the future. Out of all, I think OOo is somehow independent and is going well. MySQL is now more business oriented and no more free bits as yummy as they were some time in near past. Java is still in a state of coma, and Open Solaris: there looks something hot under the surface of calmness. Let us see what happens.