You can find more information in the DMCA notice I filed, but basically you can't claim copyright on things you didn't write or on very simple changes (e.g. claiming copyright for a two-line change holds no water) and you must state significant changes. However, you can still hold copyright on your changes if they are significant and on code you originally wrote.
Let me know if you need help applying the terms of the Apache license and I can guide you through them.
You can find more information in the DMCA notice I filed, but basically you can't claim copyright on things you didn't write or on very simple changes (e.g. claiming copyright for a two-line change holds no water) and you must state significant changes. However, you can still hold copyright on your changes if they are significant and on code you originally wrote.
Let me know if you need help applying the terms of the Apache license and I can guide you through them.