All of the acceptions you have listed are currently in use, but don't forget that the reading/meaning you choose often has a lot to do with what particular group or groups you want to belong to. Apparently the Java people at your work belong to a group that considers the word "hack" to be pejorative. You see yourself as belonging to a group of people that consider "hack" to be positive. When you use "hack" in this sense, you are socially setting yourself apart from your co-workers.

The English language is big enough for all of these meanings, but you'll find that people typically are not at all familiar with the use of "hack" in any positive sense. That sense is reserved to another in-group. That means you might have to translate what you mean when you're talking to people who either don't know or don't accept your definition.

This is a bit of an aside to the whole topic:
As far as dictionaries are concerned, there are a number of philosophies that dictate how they choose the meanings listed under each word and how those items are ordered. Some dictionaries have a descriptive character, trying to show how language is used. Others have a prescriptive nature, reflecting their editors' linguistic preferences. Unfortunately, it's really hard to tell which ones are which.

Here's the entry for hacker from WordNet 2.0:

hacker
n 1: someone who plays golf poorly
2: a programmer who breaks into computer systems in order to steal or change or destroy information as a form of cyber-terrorism [syn: {cyber-terrorist}, {cyberpunk}[]]
3: a programmer for whom computing is its own reward; may enjoy the challenge of breaking into other computers but does no harm; "true hackers subscribe to a code of ethics and look down upon crackers"
4: one who works hard at boring tasks [syn: {hack}, {drudge}[]]

WordNet concentrates on descriptive definitions.