Jainism and Buddhism is very different... they believe in a
soul, which is absent in Buddhism. The other core teachings are
also different. There is a sutta in which Buddha debated against
the Jainist understanding of karma.
Anyone who believes Buddhism is a creation of Jainism, or that
they have even the slighest similar origins, is a fool.
The only similarities between Jainism and Buddhism is the
rejection of the Vedic texts as authority. This made both Jainism
and Buddhism 'unorthodox' traditions in India. Jainism and Buddhism
both has Sramana (the tradition of wandering monks/ascetics) rather
than Brahmanical roots. Both Jainism and Buddhism also came from a
similar time period - but so are some other religions, like Lao Tzu
of Taoism.
p.s. on Buddha's rejection of Jainist teachings,
Strong emphasis on the doctrine of karma and intense
asceticism was also criticised by the Buddhists, even though they
also believe in karma. The ancient Buddhist scripture
Saṃyutta Nikāya
narrates the story of Asibandhakaputta, a headman who was
originally a disciple of Māhavīra. He
debates with the Buddha, telling
him that, according to Māhavīra (Nigaṇṭha Nātaputta), a man's fate
or karma is decided by what he does habitually. The Buddha
responds, considering this view to be inadequate, stating that even
a habitual sinner spends more time "not doing the sin" and only
some time actually "doing the sin."[98]
In another Buddhist text Majjhima Nikāya,
the Buddha criticizes Jain emphasis on the destruction of
unobservable and unverifiable types of karma as a means to end
suffering, rather than on eliminating evil mental states such as
greed, hatred and delusion, which are observable and
verifiable.[99]
In the Upālisutta dialogue of this Majjhima Nikāya text,
Buddha contends with a Jain monk who asserts that bodily actions
are the most criminal, in comparison to the actions of speech and
mind. Buddha criticises this view, saying that the actions of
mind are most criminal, and not the actions of speech or
body.[100]
Buddha also criticises the Jain ascetic practice of various
austerities, claiming that he, Buddha, is happier when not
practising the austerities.[101][note
8]