This is normally impossible, as OpenComputers hides item Nbt data by default (to ensure no one can read possible secret data that is hidden in the nbt data)
You can, however, change config option 'allowItemStackNBTTags' inside 'vanilla' inside 'integration' to 'true', allowing you to read the NBT data in GZIP format. However, the data card uses ZLIB. Fortunately, from what I can find, GZIP is basically ZLIB with a header, so it shouldn't be hard to make a program that ignores the header and then decompresses it as ZLIB.