Results of action are of four types:
1) utpAdya – a result in the form of a product, like a pot.
2) Apya – a result in the form of reaching, like going abroad or to heaven.
3) saMskArya – a result in the form of removal of impurity and imparting a good qualiity.
4) vikArya – a result in the form of modification, e.g. milk to yoghurt.
Making, reaching, purifying and modifying are the four results obtained by karma. mokSha (enlightenment) is not a product because it is nitya (eternal). It cannot be reached because it is you. It cannot be purified because it is free from blemish. It cannot be modified because it is one whole. Hence, nitya-mokSha is not a product or by-product of karma.
muNDakopaniShad (Vol. 1), Swam Dayananda Saraswati, Arsha Vidya Centre. ISBN 81-903636-3-8.