The floating point package of Limbo provides control of exceptions, and there are other differences as well, even though the basic libraries cover the same ground in both languages. Another difference, that is not directly related to the syntactical features of the languages, is the implementation of the virtual machine. For the same reason, the Dis interpreter is also much smaller than the Java virtual machine. JavaOS implements the Java Base Platform, and iincludes the Java Virtual Machine, the Java Embedded API, and underlying functionality for windowing, networking, and the file system. This advantage does not apply for normal microprocessors, though, and it might take a while before these specialized microprocessors are mass-products.
Inferno is a much cleaner concept, and more generic.
The hype-factor surrounding Java works in the favour of Java, at least for know, but unless some serious office automation software appears soon, Java might lose its current edge in the market. Limbo continues the C tradition of using a lot of special characters and combination of them to achieve syntactical shortness, while Java is sprinkled with magical keywords.