This program is error free. Or error-free?
Solution 1:
According to the Chicago Manual of Style § 7.89(3), "[c]ompounds formed with free as second element are hyphenated both before and after a noun." The examples given are "toll-free number" and "accident-free driver."
Specifically, in the construction you listed, the examples are:
"The number is toll-free." and "The driver is accident-free."
Therefore, "The program is error-free." would be the proper construction under the Chicago Manual though other style-guides may say otherwise.